HP-71B: 1^Inf Error

[J-F Garnier]

I only recently noticed that the HP-71B is raising an error when attempting to calculate 1^Inf.
This result is, at first glance, a bit surprising so I wanted to check on other machines.

The next high-end machines after the 71B were the 28C/S then the series 48 but none were supporting the infinite quantity any more, or other 71B features such as NaN, denormalized numbers and signed zero. Actually these quantities may still result from internal calculations but are not exposed to the user. Maybe because HP thought it was too complicate for most users, with too little benefit.

So we have to jump to the 49G (1999, so 15 years later) to find another HP calculator with direct support of the infinite quantity.
And indeed, the 49G also returns an undefined result ('?') for 1^Inf.
On the other hand, the contemporary TI-89 has no problem to calculate 1^Inf = 1 , but of course returns an undefined result for (-1)^Inf.

They may be good mathematical arguments to consider 1^Inf as undefined, but it's not what I'm mostly interested in.
I'm more curious of the reasons of the HP-71B development team: pure mathematical considerations or implementation constraints?
The choice they made at the time propagated to the next machines for several decades.

J-F